In a manufacturing process for manufacturing semiconductor devices, liquid crystal panels, LEDs, solar cells or the like, a process gas is introduced into a process chamber which is being evacuated to perform various processes such as an etching process or a CVD process. The process chamber for performing various processes such as an etching process or a CVD process is evacuated by a vacuum pump. Further, the process chamber and exhaust apparatuses connected to the process chamber are cleaned periodically by supplying a cleaning gas thereto. Because exhaust gases such as the process gas and the cleaning gas contain a silane-based gas (SiH4, TEOS or the like), a halogen-based gas (ClF3, HF, F2, HCl, Cl2 or the like), a PFC gas (CF4, C2F6, NF3, SF6 or the like) or the like, such exhaust gases have negative effects on human bodies and on the global environment such as global warming. Therefore, it is not preferable that these exhaust gases are emitted to the atmosphere as they are.
Accordingly, these exhaust gases discharged from the process chamber are treated to be made harmless by an exhaust gas treatment apparatus, and the harmless exhaust gases are emitted to the atmosphere. In this case, exhaust systems equipped with the exhaust gas treatment apparatus are classified broadly into a system in which the exhaust gas treatment apparatus is arranged at an immediately downstream side of the process chamber and the vacuum pump is arranged at a downstream side of the exhaust gas treatment apparatus, i.e., a system in which the process chamber, the exhaust gas treatment apparatus, and the vacuum pump are arranged in this order; and a system in which the vacuum pump is arranged at an immediately downstream side of the process chamber and the exhaust gas treatment apparatus is arranged at a downstream side of the vacuum pump, i.e., a system in which the process chamber, the vacuum pump, and the exhaust gas treatment apparatus are arranged in this order. In the vacuum pump, a single vacuum pump may constitute an exhaust system, or a booster pump and a main pump may be connected to constitute an exhaust system.
The above system in which the process chamber, the exhaust gas treatment apparatus, and the vacuum pump are arranged in this order has the following problems: When operation of the exhaust gas treatment apparatus is stopped due to its breakdown or the like, or the operation of the exhaust gas treatment apparatus is stopped even in its normal operation state, products generated by exhaust gas treatment flow back to the process chamber to contaminate the process chamber.
On the other hand, the system in which the process chamber, the vacuum pump, and the exhaust gas treatment apparatus are arranged in this order has no problem that products generated by exhaust gas treatment flow back to the process chamber to contaminate the process chamber, because the vacuum pump is arranged between the process chamber and the exhaust gas treatment apparatus. Therefore, this system is widely used as a stable exhaust system.
However, the above system in which the process chamber, the vacuum pump, and the exhaust gas treatment apparatus are arranged in this order has the following problems: Since a purge gas and a diluent gas are introduced at an upstream side of the exhaust gas treatment apparatus, the exhaust gas treatment apparatus is required to treat the exhaust gas containing the purge gas and the diluent gas, and thus the amount of gas to be treated becomes large and the amount of energy inputted for exhaust gas treatment becomes large.
Conventional exhaust gas treatment apparatuses, including the above two systems, have the following problems.
1) The exhaust gas treatment apparatus is large in size and needs to be installed fixedly in a factory. Since it is difficult and costly to transport the exhaust gas treatment apparatus that has been installed fixedly, the exhaust gas treatment apparatus has been designed so that maintenance can be performed on site. On the other hand, in order to realize on-site maintenance, component parts such as a motor and a controller are designed to be detachable, and thus the exhaust gas treatment apparatus as a whole becomes expensive and large in size.2) Since the exhaust gas treatment apparatus is installed fixedly and difficult to be replaced, at the time of breakdown of the apparatus, the process has been forced to be shut down until the completion of repair of the apparatus.3) Since the exhaust gas treatment apparatus has been designed in accordance with the kind and flow rate of inflow gas, a large amount of work of design, manufacturing, and evaluation has been required.4) Although the exhaust gas treatment apparatus has a function to treat the introduced gas, such exhaust gas treatment apparatus has not been designed to grasp connection status with another exhaust gas treatment apparatus. Therefore, in order to construct back-up, an additional control apparatus for collectively controlling, a plurality of exhaust gas treatment apparatuses has been needed.5) Since the vacuum pump and the exhaust gas treatment apparatus are independent apparatuses and have respective controllers, operational manipulation, daily maintenance, analysis of histories at the time of trouble, and the like of them have been conducted individually, thus requiring troublesome and time-consuming work.6) In order to avoid deposition of products in the pipe caused by cooling of the gas to be exhausted, the pipe interconnecting the vacuum pump and the exhaust gas treatment apparatus has been heated by using a heater. Thus, initial cost and running cost for the heater have been required.7) In order to avoid deposition of products, in the connecting portion between the booster pump and the main pump, caused by cooling of the gas to be exhausted, the connecting portion has been heated by a heater or has been covered with a thermal insulator.8) In order to avoid deposition of products, in the interior of the booster pump, caused by cooling of the gas to be exhausted, the booster pump has been heated by a heater or has been covered with a thermal insulator.